It is well known that toner and/or carrier particles used in electrophotographic developing processes are required to possess certain characteristics. In developing and transfer processes, the toner behaves as charged particles. In two-component developing materials, the charge is triboelectrically imparted to the toner by contact with the carrier, while in monocomponent developing materials, the charge is triboelectrically imparted to the toner through contact with a developing sleeve or other member of the developing device. That is, the toner and/or carrier must possess triboelectric charging properties. The toner and carrier particles function as a fluid when the toner is supplied to the developing device and residual toner is cleaned from the photosensitive member. The carrier functions to carry the toner to the developing region. Further, the toner and/or carrier particles must possess flow characteristics. In addition, the various aforesaid properties must be evident under a variety of environmental conditions, so that the toner and/or carrier must be resistant to environmental influences.